Do you believe in karma? Do you think that if you do a good deed that the universe will pay you back in some form, and vice versa? If not, what is your arguement against it?

I think believing in karma offers a way of living that allows you to look at your choices more closely and that if you believe your a good person, it can be a tool when times are rough that things will get better, a bit of hope if you will.

I used to be a firm believer in karma when I was in high school, but I'm not too sure where I stand anymore.